DevTools: Show metrics in styles tab of styles sidebar in undocked/docked to bottom mode.

BUG=278332
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/23392004

git-svn-id: svn://svn.chromium.org/blink/trunk@156711 bbb929c8-8fbe-4397-9dbb-9b2b20218538